In a motor vehicle where battery voltage is subject to variation over a large range, say, 4.5 volts to more than 10 volts, a boost power supply is used to provide a consistent voltage, say, about 10 volts, to drive electronic circuits. In one type of boost supply an inductor coupled to battery voltage has its current interrupted by a switch in a manner which induces voltage greater than the battery voltage. The resulting inductor current charges a capacitor up to a desired output voltage where the switching is suspended. A switch frequency is chosen to yield the necessary output voltage when the battery voltage is low. The peak current flowing through the switch is proportional to the battery voltage so that at high battery voltages high inductor currents are present and may lead to undesirable inductor saturation. These higher inductor saturation currents also flow through the switch which is typically a transistor and cause excessive power dissipation in the switch.
The problem of damaging components can be avoided by using a more expensive inductor with a higher current rating which will not saturate at high voltages. The extra expense in an electronic package is highly undesirable. Thus a solution is preferred which is inexpensive.